The field of the disclosure relates generally to structural health monitoring of composite structures, and more specifically, to methods and systems for multi-ferroic structural health monitoring.
Composite materials are attractive for aerospace structural applications because of their high strength to weight ratios compared to metals. Particularly, composite materials are increasingly utilized in a wide variety of applications, including for aircraft structures. Composite aircraft structures include mixtures of bonded and bolted laminates with a variety of metallic and composite substructures. Other examples include composite sandwiched structures and other adhesive bonded panels including assemblies and structures with contoured surfaces.
Further improvements in composite structure affordability can be realized through low-cost and light weight structural health monitoring systems. Degradation of the composite laminate itself, due to impacts, lightning damage, thermal damage, or micro-cracking can be managed with condition-based-maintenance, reducing costs for non-destructive inspection (NDI), especially in limited access areas where disassembly is required.
Non-destructive evaluation (NDE) methods currently used to inspect bonded structures include modified pulse-echo ultrasonic testing (UT), infrared thermography, shearography, eddy current testing, and various high and low frequency ultrasonic methods.
Structural health monitoring (SHM) of composite and bonded structures has focused primarily on networks of piezo-electric sensors sending and receiving ultrasonic waves that interrogate the structure, or embedded fiber optic sensors measuring strain, moisture, temperature, and the like. Traditional nondestructive inspection methods rely upon quantifying defects within the structure to predict the flightworthiness of the structure. However, these inspection methods may be unable to ascertain the cohesiveness of the bond at any location absent defects. Further, piezo-electric and fiber optic-based SHM methods have limitations related to the embedding of the sensors, connectivity of the sensors, and costs for the supporting systems.
It remains desirable to inspect such structures to identify any defects, such as cracks, discontinuities, voids, or porosity, which could adversely affect the performance of the structure.